This application is based on and claims the priorities under 35 U.S.C. xc2xa7119 of German Patent Application 101 01 916.5, filed on Jan. 16, 2001 and German Patent Application 101 34 852.5, filed on Jul. 18, 2001, the entire disclosures of which are incorporated herein by reference.
The invention relates to a holding apparatus for holding large format workpieces, in the manner of a flexible and adaptable clamping jig system including plural workpiece support units. The invention further relates to a method of mounting and holding large format workpieces so that the workpieces may be machined or worked on with a suitable machine tool system that cooperates with the holding apparatus.
Flexible or adaptable workpiece clamping and holding systems are known in the art, for example from the German Patent Publication DE 197 45 145 A1. Disclosed therein is a machine for holding workpieces, whereby the machine comprises several units that comprise arches which are movable along rails. Several of such arches are provided for receiving one or more large format workpieces. The two outermost arches of such a support unit are fixedly connected with the rails, and the entire support unit is transportable and repositionable using a loading crane for carrying out assembly processes. A workpiece (or several such workpieces), is fixed or clampingly mounted on the support unit, and is then pushed into a riveting machine along a further rail system, and the unit is then secured in a rigid or fixed position.
In the known system, to avoid a collision between elements of the riveting machine and elements of the holding system during the riveting process, the respective affected arches can be repositioned or moved to a different position. For this purpose, telescope rods are retracted and the affected arch is moved away along the rails. During this time, the riveting process is interrupted and is in a resting state or standstill. It is further disadvantageous that moving away the respective arch in this manner results in a complete removal of the support and clamped fixing of the workpiece in the entire region or area of the freed arch. After the riveting process is completed, the entire workpiece carrier is pushed out of the riveting machine, and further working or processing steps can be carried out on the workpiece, or the workpiece carrier is transferred or shifted and the workpiece is dismounted from the carrier unit.
Thus, in general, the known holding apparatuses of the above general type have been developed and built on the basis of existing support or carrier systems in the context of the relevant installation technology, for example utilizing exchange and/or positioning frames, apparatus rigging scaffolds, joining stations, portal systems, assembly or rigging table systems, and the like. To some extent, the assembly and positioning processes must be developed and carried out according to complex technical and time-based control schemes. Moreover, high capital investments in the installation technology have been necessary, especially when a large spectrum of workpieces with various different dimensions and configurations is to be handled. The final outfitting or equipping of the installation is typically carried out through the use of further subsystems such as work platform structures, transfer carriages, lift platforms, conveyor baskets, and the like. In this context, a rather high logistic effort must be carried through, especially due to the large dimensions of the workpieces (for example approximately up to a size of 11 mxc3x973 m for the skin fields or panels of an aircraft fuselage), and due to the possible curvatures of the large format workpieces that are to be joined together.
In view of the above, it is an object of the invention to provide an apparatus for holding large format workpieces, which avoids the use of rigid or fixed carrier systems with geometrically determined apparatuses or devices, and thereby reduces the complexity, effort and investment in the installation technology. A further object of the invention is to achieve a flexibly adaptable stressed or clamped holding and support of workpieces of various different forms and sizes using the same basic holding apparatus. The invention further aims to avoid or overcome the disadvantages of the prior art, and to achieve additional advantages, as apparent from the present specification.
The above objects have been achieved according to the invention in a holding apparatus for holding large format workpieces, including plural workpiece support units that are movable along a rail system. One set of some of the workpiece support units is arranged along one side of the workpiece, while a second set of the other ones of the workpiece support units is arranged along the other side of the workpiece. At least some of the workpiece support units respectively comprise support arms that are movable and pivotable on a support column. In order to make space for a working machine or machine tool system such as a riveting machine, so that the machine may carry out a work cycle in the area of one of the workpiece support units, a minimum number of support arms is movable out of the working area of the machine, while the greatest possible number of support arms of the respective workpiece support units continue to simultaneously support and hold the workpiece. The holding is often referred to as xe2x80x9cclampingxe2x80x9d herein, which relates to the overall clamped or positively held and supported condition of the workpiece, but does not require that each support arm must actually use a clamp to hold the workpiece. Instead, the holding may be achieved by any conventionally known fixture for holding such a workpiece, and preferably according to the invention the holding is achieved by suction units on the support arms, while clamp members are provided on the outermost support units.
According to further detailed features of the invention, the outermost ones of the workpiece support units are embodied as a respective front and rear clamping support bridges, with support arches supported on both sides in respective support columns. The support bridges extend archingly entirely across the support area for supporting the workpiece between the two respective support columns, while the support arms of the other workpiece support units each only extend partially across the width of the support area. Clamping units and at least one fixing unit may be provided on at least one of the support bridges for respectively clampingly holding the end edges of the workpiece and for precisely positioning the workpiece in connection with a predefined receiver hole in the workpiece.
At least one individual mounting fixture is provided on the support arm of each workpiece support unit. The support arm is preferably movably arranged on and connected to the respective support column, which in turn is movable in a direction parallel to the main machining axis or working direction. By the appropriate movement of the support arms, the workpiece support units provide at least one loading position and one working position, whereby the workpiece support units are height adjustable in the working position, in order to form an access space below the support arms or support bridges. The support arms can, individually and independently of each other, be released from the workpiece and moved out of the working area or working range of the machine, such as a riveting machine, so as to provide the necessary working space for the machine.
The above objects have further been achieved according to the invention in a combination of the inventive holding apparatus and a workpiece machining or working machine, such as an orbital riveting machine including an upper tool and a lower tool, whereby the machine can move with its upper tool over the workpiece support units, and with its lower tool between and laterally past the support columns of the workpiece support units.
Still further, the above objects have been achieved according to the invention in a method of machining or working on a large format workpiece using the inventive combination of the holding apparatus and the working machine. The workpiece support units are moved into the loading position, in which the support arms of the workpiece support units in at least one row are tilted upwardly. The workpiece is set onto an outer load receiver and then laid against an inner load receiver of each respective support arm. Then the workpiece is released from the workpiece feed or supply apparatus and is carried only by the holding apparatus. Thereafter, the upwardly pivoted support arms are lowered until a contact support of the workpiece on the other row of workpiece support units is achieved. Then the workpiece is fixed and clamped along its lateral edges, whereby the workpiece is supported and held by the workpiece mounting fixtures. Then, while the machining or other working process such as a riveting process is carried out, and the support units are in the working position, a minimum number of the support arms is moved out of the working range or zone of the tools of the working machine, so as to provide the necessary space for the machine to carry out a work cycle in the area of one of the support arms, while the greatest possible number of the remaining support arms simultaneously continue to support the workpiece.
The apparatus and the method according to the invention make it possible to react and correspondingly adapt the apparatus and the method flexibly to varying requirements during the fabrication or assembly process, for example a readjustment to different workpiece dimensions or the like. It also becomes possible to reduce the mounting, rigging or setup time. The following advantages are also achieved: avoiding the use of a carrier system, and especially a fixed carrier system; avoiding the use of subsystems; improving the ergonomics of the mounting or rigging processes; increasing the flexibility and adaptability of the clamping support system, for example using a tower or column based solution; using additional possible auxiliary axes; and being able to handle a large spectrum of workpieces with the largest possible dimensions, for example in terms of the spherical dimensions or the bulging or humping dimensions of the workpieces.